As disclosed in U.S. Patent 3,255,272 (Lindsay), it is known that alkenes can be dimerized in the presence of alkali metal hydroxide-promoted alkali metal catalysts, which may be supported or unsupported, although the patentee appears to indicate that the supported catalysts are inferior to unsupported catalysts in the reactions. Such processes are of interest for the dimerization of alkenes in general, but they are of particular interest for the dimerization of normal 1-alkenes containing 3-8 carbons, especially propene.
The dimerization of propene typically results in the formation of a mixture of hexenes, one of which is 4-methylpentene-1, a compound which is useful as a fuel additive and as a monomer which can be employed to prepare desirable homopolymers and copolymers. The more attractive propene dimerizations are those which maximize the amount of 4-methylpentene-1 formed.
In the dimerization of alkenes, one molecule of an alkene is coupled with another molecule of the same alkene. Other alkene coupling reactions of interest are those in which one molecule of an alkene is coupled with a molecule of a different alkene, as in the coupling of propene and ethene to form pentene-1.